Using Verizon DSL - occasionally it loses internet connection. Powering it off and on restores the connection - this has been happening as long as I have been using Verizon DSL and has never been an e-mail problem in the past.

Perhaps there was an update to Outlook which is causing this behavior.

Also, check the properties on your network adapter. I have often found that the default setting is to turn it off when not in use, which could cause you to have to reestablish the connection (i.e. "log back in") when you send a message. Make sure it is set to stay on all the time.